1. Field of the Invention
The present invention relates to a trench gate type power device that suppresses latchup in the event of a short circuit or the like and has high withstand voltage characteristics.
2. Background Art
Power devices are high withstand voltage semiconductor devices widely used for power control. Among power devices, IGBTs (Insulated Gate Bipolar Transistors) are excellent in the ability to miniaturize a cell structure and realize a high withstand voltage device or the like.
An IGBT is provided with a p-type base region on a surface and a p-type collector region on a rear surface of an n-type semiconductor substrate which is a conductivity modulation region. An n-type emitter region is formed on a surface of the base region. Trench gates are formed in a plurality of longitudinal trench grooves formed so as to penetrate the aforementioned emitter region.
Patent Document 1 discloses a semiconductor apparatus in which a contact hole is formed between a trench gate and another trench gate. As described in FIG. 3(f) of Patent Document 1, a p+ layer called “low resistance region” is formed on an inner wall of the aforementioned contact hole by thermal diffusion. The aforementioned p+ layer has an effect of reducing base resistance. Therefore, even when a back electromotive force is given between a source (emitter) and a drain (collector), a parasitic transistor made up of a source region, channel region and epitaxial layer does not easily turn ON. Thus, the configuration in FIG. 3(f) of Patent Document 1 can increase a withstand voltage.    Patent Document 1: Japanese Patent Laid-Open No. 2004-303964    Patent Document 2: Japanese Patent Laid-Open No. 2004-095962    Patent Document 3: Japanese Utility Model Laid-Open No. S63-124762    Patent Document 4: Published Japanese translations of PCT international publication for patent applications No. 2007-500454    Patent Document 5: Japanese Patent Laid-Open No. 2000-058823    Patent Document 6: Japanese Patent Laid-Open No. 2002-353456